Deconstructing the Dimensions of Mycobiome Fingerprints in Luohandu Cave, Guilin, Southern China.

Subterranean karst caves are windows into the terrestrial subsurface to deconstruct the dimensions of mycobiome fingerprints. However, impeded by the constraints of remote locations, the inaccessibility of specimens and technical limitations, the mycobiome of subterranean karst caves has remained largely unknown. Weathered rock and sediment samples were collected from Luohandu cave (Guilin, Southern China) and subjected to Illumina Hiseq sequencing of ITS1 genes. A total of 267 known genera and 90 known orders in 15 phyla were revealed in the mycobiomes. Ascomycota dominated all samples, followed by Basidiomycota and Mortierellomycota. The sediments possessed the relatively highest alpha diversity and were significantly different from weathered rocks according to the diversity indices and richness metrics. Fifteen families and eight genera with significant differences were detected in the sediment samples. The Ca/Mg ratio appeared to significantly affect the structure of the mycobiome communities. Ascomycota appeared to exert a controlling influence on the mycobiome co-occurrence network of the sediments, while Ascomycota and Basidiomycota were found to be the main phyla in the mycobiome co-occurrence network of weathered rocks. Our results provide a more comprehensive dimension to the mycobiome fingerprints of Luohandu cave and a new window into the mycobiome communities and the ecology of subterranean karst cave ecosystems.

Non-ionic polysorbate surfactants: alternative inducers of medium-chain-length poly(3-hydroxyalkanoates) (MCL-PHAs) for production of extracellular MCL-PHA depolymerases.

The potential of non-ionic polysorbate surfactants as alternative inducers of medium-chain-length poly(3-hydroxyalkanoates) (MCL-PHAs) for the production of diverse bacterial MCL-PHA depolymerases was evaluated. When grown with corn oil as the sole carbon substrate, Pseudomonas alcaligenes LB19 preferentially produced lipolytic enzymes, but its MCL-PHA depolymerase was not induced by the substrate. However, the results of activity staining and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis clearly revealed that Tween 20 induced simultaneous production of lipolytic enzymes and the MCL-PHA depolymerase with the molecular mass (26.5 kDa) of P. alcaligenes LB19, which has been previously identified. Moreover, the co-production of two functionally distinct hydrolytic enzymes induced by Tween 20 was commonly observed in various Gram-positive and Gram-negative bacteria that were fed the substrate. Thus, it is expected that non-ionic polysorbate surfactants including Tween 20 can be widely exploited as promising universal substrates for the facile and efficient production of diverse MCL-PHA depolymerases.

Production of medium-chain-length polyhydroxyalkanoates by activated sludge enriched under periodic feeding with nonanoic acid.

The potential use of activated sludge for the production of medium-chain-length polyhydroxyalkanoates (MCL-PHAs) was investigated. The enrichment of bacterial populations capable of producing MCL-PHAs was achieved by periodic feeding with nonanoic acid in a sequencing batch reactor (SBR). Denaturing gradient gel electrophoresis analysis revealed Pseudomonas aeruginosa strains to be predominant in the bacterial community during the SBR process. The composition of PHA synthesized by the enriched biomass from nonanoic acid consisted of a large concentration (>89 mol%) of MCL monomer units and a small amount of short-chain-length monomer units. Under fed-batch fermentation with continuous feeding of nonanoic acid at a flow rate of 0.225 g/L/h and a C/N ratio of 40, a maximum PHA content of 48.6% dry cell weight and a conversion yield (Y(p/s)) of 0.94 g/g were achieved. These results indicate that MCL-PHA production by activated sludge is a promising alternative to typical pure culture approaches.

Biosynthesis of medium-chain-length poly(3-hydroxyalkanoates) by volatile aromatic hydrocarbons-degrading Pseudomonas fulva TY16.

Pseudomonas fulva TY16 biosynthesized medium-chain-length poly(3-hydroxyalkanoates) (MCL-PHAs) containing unsaturated 3-hydroxydodecenoate unit (approximately 8-9%) when grown with volatile aromatic compounds including benzene, toluene, and ethylbenzene as sole carbon substrate. In particular, when cultivated using a continuous feeding system designed to supply toluene at a flow rate of 0.42gL(-1)h(-1) into a 7-L jar fermentor, the growth of the organism reached up to approximately 3.87gL(-1) after the 48h fed-batch fermentation, representing an accumulated cellular MCL-PHA of 58.9% by weight. The obtained MCL-PHA was a copolyester primarily consisting of 3-hydroxydecanoate (55.2%) and 3-hydroxyoctanoate (26.8%) with minor constituents being 3-hydroxyhexanoate (3.7%), 3-hydroxydodecenoate (8.2%), and 3-hydroxydodecanoate (6.1%). The present results suggest that P. fulva TY16 is a promising candidate for the biotechnological conversion of toxic petrochemical wastes to valuable biopolymers.